The candidate's long-term goal is to become an independent clinical investigator who conducts healthy lifestyle interventions that will influence the mental and physical health outcomes associated with late-life spousal bereavement. The proposed Mentored Research Scientist Development Award (K01) will provide a specialized 4-year training program that will enable the candidate to develop expertise in mental illness prevention intervention research and to effectively transition into an independent interventionist. The proposed K01 Award will ensure the candidate's successful transition to an independent interventionist by providing training in three key areas: (1) the design, development, and conduct of mental illness prevention intervention research; (2) the mechanisms by which mental health interventions protect spousally bereaved elders from mental illness; and (3) moderating and/or mediating influences that biomarkers have on the relationship between healthy lifestyle interventions and mental health outcomes. These training aims are supported by the proposed research plan, which aims to test the feasibility and acceptability of a healthy lifestyle intervention among older adults who are at risk for developing major depression, anxiety, and/or complicated grief disorder(s) following spousal bereavement. The career development activities outlined in this application align with the NIMH strategic objective 2.3 - 'to develop and test innovative interventions to reduce risk and positively alter trajectories of illness.' Approximatel 10-20% of spousally bereaved elders experience intense and prolonged emotional responses that lead to mental health problems including major depression, anxiety, and/or complicated grief disorder(s). The proposed research will evaluate the feasibility and acceptability of a healthy lifestyle intervention that uses a technology-based behavioral self-monitoring protocol to encourage engagement in physical activity, healthy eating, and good sleep practices following spousal bereavement. Data from 10 participants will be used for the development of a prevention intervention manual (Aim 1). A small pilot study will be conducted (Aim 2) in which 50 participants will be randomly assigned to 12 weeks of (1) behavioral self- monitoring using a smartphone (n=20), (2) behavioral self-monitoring using a smartphone + motivational interviewing-based lifestyle coaching (n=20), or (3) enhanced usual care (n=10). Blood samples will be collected to explore inflammatory cytokines as a potential mediator/moderator of mental health risk. The proposed K01 award will provide the candidate with the expertise to transition into an independently funded interventionist, and will allow her to gather feasibility evidence for the development of a healthy lifestyle intervention to prevent the onset or delay the progression of mental health problems among older adults experiencing late-life spousal bereavement. The proposed K01 will culminate in the development of an R01 application to conduct a larger-scale prevention trial to promote the mental health of spousally bereaved elders.